Physiologic Fluctuations of Serum Estradiol Levels Influence Biochemical Markers of Bone Resorption in Young Women

Abstract

We investigated the effect of physiologic variations in sex hormone levels during the menstrual cycle on biomarkers of bone turnover. Blood and 24-h and fasting urine samples were obtained in nine women (age, 25.1+/-3.0 yr) with regular menstrual cycles during the early follicular period (t1), 3 days before ovulation (t2), 3 days after ovulation (t3), at the midluteal period (t4) and again during the early follicular period of the next cycle (t5). All subjects had a calcium intake covering current dietary recommendations (above 1,000 mg/day, standardized food record). Serum calcium, phosphorus, calcitriol, 24-h and 2-h fasting urinary calcium, and phosphorus excretion remained constant during the menstrual cycle. Serum 25-hydroxyvitamin D3 levels decreased slightly from the beginning until the end of the study (P<0.05), indicating low cutaneous vitamin D synthesis during wintertime. The serum levels of sex hormones showed typical monthly variations, with the lowest estradiol (E2) levels at t1 and t5. Fasting 2-h pyridinoline (Pyd) concentrations (a marker of bone resorption) fell from t1 to t3 and rose again at t5 (P<0.01). Similar variations were observed for the resorption marker deoxypyridinoline (Dpd; P<0.05). The amplitude of the two biomarkers was 32% and 33%, respectively. The serum levels of the carboxyterminal propeptide of type I collagen (a marker of bone formation) showed an inverse cyclic pattern, as compared with the pyridinium cross-links. Low concentrations were observed at t1; a rise occurred until t3 and was followed by a decrease until t5 (P<0.05). A similar cyclic pattern was observed for serum PTH levels, with the highest concentrations at t3 (P<0.05). Dpd and Pyd values were significantly correlated with serum E2 levels (r = 0.52; P<0.0001 and r = 0.50; P<0.001, respectively). Neither progesterone nor LH nor FSH was correlated with Pyd or Dpd levels. The data suggest that normal menstrual cycling in young women is associated with monthly fluctuations in bone turnover. This physiological effect of the menstrual cycle is most probably related to variations in serum E2 concentrations.

Serum Inorganic Phosphorus, Uric Acid, Calcium, Magnesium and Sodium Status During Uterine Changes of Menstrual Cycle

“…Similar results were also observed by other authors [22,25]. The raised estrogen levels possibly by acting through parathyroid hormone could be responsible for depicting the body stores of magnesium by decreasing the reabsorption of magnesium ions by the renal tubules thus resulting in midcycle decline 29 . In Table- 30,31 .…”

Lower body negative pressure treadmill exercise as a countermeasure for bed rest-induced bone loss in female identical twins

“…Biochemical markers of bone resorption are clearly influenced by fluctuations in these hormones [10,23,48]. In one study, PYD varied as much as 50% from 3 days after ovulation to day 3 of the follicular period of the same menstrual cycle [48]. Because menstrual cycles were not controlled for in the present study, this variability with sex hormone fluctuations (Fig.…”

“…Much of the variability is likely to be related to cyclic fluctuations of female sex hormones. Biochemical markers of bone resorption are clearly influenced by fluctuations in these hormones [10,23,48]. In one study, PYD varied as much as 50% from 3 days after ovulation to day 3 of the follicular period of the same menstrual cycle [48].…”

Comparative Study of Hematological and Biochemical Parameters during Different Phases of Menstrual Cycle in Young Healthy Women Aged 18-22 Years

“…The levels of serum magnesium in present study were significantly highest during the luteal phase and lowest during the follicular phase. The raised estrogen levels possibly by acting through parathyroid hormone could be responsible for depicting the body stores of magnesium by decreasing the reabsorption of magnesium ions by the renal tubules thus resulting in midcycle decline 5 . Therefore, it is suggested that calcium/magnesium ratio may be related to the premenstrual syndrome complaints that some women have during this period 34 .…”